Wavefront Correction Method for Adaptive Optics System

ABSTRACT

A method, controller, and medium to control an adaptive optics scanning laser ophthalmoscope. Receiving from the ophthalmoscope a plurality of wavefront elements. Each element may be associated with an area of a beam of light received from a fundus. Each element includes shape data. The shape data represents a shape of a wavefront in a area of the beam. Each element includes status data. The status data is a confidence indicator of ability of the shape data to represent the shape of the wavefront with a particular level of accuracy. Calculating control data based on the shape data in the wavefront data and local gain. The local gain includes local gain elements. Each local gain elements is adjusted based on status data. Using the control data to adjust a shape of an illumination wavefront of an illumination beam used to illuminate the fundus.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation, and claims the benefit, of U.S. patentapplication Ser. No. 15/099,435 filed Apr. 14, 2016. U.S. patentapplication Ser. No. 15/099,435 is hereby incorporated by referenceherein in its entirety.

BACKGROUND Field of Art

The present disclosure relates to a system and method for controlling anadaptive optics system for an ophthalmic apparatus.

Description of the Related Art

Ophthalmoscopes, ophthalmic image pickup apparatuses, fundus imagingsystems such as: scanning laser ophthalmoscopes (SLOs) that irradiatethe fundus with a laser in two dimensions; and optical coherencetomographs (OCTs) that utilizes the interference of low coherence lighthave been developed and commercialized. Thus, SLOs and OCTs have becomeimportant tools for the study of the human fundus in both normal anddiseased eyes.

The resolution of such ophthalmic image pickup apparatuses has recentlybeen improved by, for example, achieving high numerical aperture (NA) ofirradiation laser light. However, when an image of the fundus is to beacquired, the image must be acquired through optical tissues includingthe cornea and the crystalline lens. As the resolution increases, theaberrations of the cornea and the crystalline lens have come tosignificantly affect the quality of acquired images.

AO-SLO and AO-OCT in which the adaptive optics (AO) are a correctionoptical system that measures the aberration of the eye and corrects forthe aberration have been pursued to improve the resolution of thesesystems. The AO-SLO and AO-OCT generally measure the wavefront of theeye using a Shack-Hartmann wavefront sensor system. A deformable mirroror a spatial-phase modulator is driven to correct the measuredwavefront, and an image of the fundus is acquired, thus allowing AO-SLOand AO-OCT to acquire high-resolution images.

SUMMARY

An embodiment is a method for a controller to control an adaptive opticsscanning laser ophthalmoscope. The method may comprise receiving fromthe ophthalmoscope a first set of wavefront data comprising a pluralityof wavefront elements. Each particular wavefront element may beassociated with a particular area of a received beam of light receivedfrom a fundus being imaged by the ophthalmoscope. Each particularwavefront element may include wavefront shape measurement data. Thewavefront shape measurement data may be representative of a shape of awavefront of the received beam of light in a particular area of thereceived beam of light. Each particular wavefront element may alsoinclude status measurement data. The status measurement data may be aconfidence indicator of ability of the wavefront shape measurement datato represent the shape of the wavefront of the received beam of light inthe particular area of the received beam of light with a particularlevel of accuracy. The method may also comprise calculating a second setof control data based on the wavefront shape measurement data in thewavefront data and a third set of local gain. The third set of localgain may include a plurality of local gain elements. Each element amongthe plurality of local gain elements may be adjusted based on one ormore of the status measurement data. The method may also comprisetransmitting the second set of control data to the ophthalmoscope. Theophthalmoscope uses the second set of control data to adjust a shape ofan illumination wavefront of an illumination beam used to illuminate thefundus.

In some embodiments calculating the second set of control data mayinclude using the following equation:

$\mspace{20mu} {x = {{G_{1}{{B\left( {sG}_{2} \right)}\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\\vdots \\x_{n}\end{bmatrix}}} = {{G_{1}\begin{bmatrix}B_{1,1} & B_{1,2} & B_{1,3} & \cdots & B_{1,m} \\B_{2,1} & B_{2,2} & B_{2,3} & \cdots & B_{2,m} \\B_{3,1} & B_{3,2} & B_{3,3} & \cdots & B_{3,m} \\\ldots & \ldots & \ldots & \ddots & \ldots \\B_{n,1} & B_{n,2} & B_{n,3} & \cdots & B_{n,m}\end{bmatrix}}\left( {\begin{bmatrix}s_{1} \\s_{2} \\s_{3} \\\vdots \\s_{m}\end{bmatrix}\begin{bmatrix}G_{2_{1}} & 0 & 0 & \ldots & 0 \\0 & G_{2_{2}} & 0 & \ldots & 0 \\0 & 0 & G_{2_{3}} & \ldots & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \ldots & G_{2_{m}}\end{bmatrix}} \right)}}}$

The matrix x may be representative of the second set of control data.The matrix B may be representative of a command matrix. The matrix s maybe representative of the wavefront shape measurement data in the firstset of wavefront data. Each wavefront shape element s_(i) may beassociated with the wavefront shape measurement data associated withelement i and may be representative of the wavefront shape in aparticular area i of the received beam of light. The matrix G₂ may berepresentative of the local gain based upon the status measurement datain the first set of wavefront data. Each local gain element G₂ _(i) maybe calculated based upon status measurement data associated with theparticular area i. The value G₁ may be representative of a global gain.

In some embodiments, calculating the second set of control data mayinclude using the following equation:

$\mspace{20mu} {x = {{{G_{1}({Bs})}{G_{3}\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\\vdots \\x_{n}\end{bmatrix}}} = {{G_{1}\begin{bmatrix}B_{1,1} & B_{1,2} & B_{1,3} & \cdots & B_{1,m} \\B_{2,1} & B_{2,2} & B_{2,3} & \cdots & B_{2,m} \\B_{3,1} & B_{3,2} & B_{3,3} & \cdots & B_{3,m} \\\ldots & \ldots & \ldots & \ddots & \ldots \\B_{n,1} & B_{n,2} & B_{n,3} & \cdots & B_{n,m}\end{bmatrix}}\left( {\begin{bmatrix}s_{1} \\s_{2} \\s_{3} \\\vdots \\s_{m}\end{bmatrix}\begin{bmatrix}G_{3_{1}} & 0 & 0 & \ldots & 0 \\0 & G_{3_{2}} & 0 & \ldots & 0 \\0 & 0 & G_{3_{3}} & \ldots & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \ldots & G_{3_{n}}\end{bmatrix}} \right)}}}$

The matrix x may be representative of the second set of control data.Each control data element k may be used to adjust the shape of theillumination wavefront in a particular illumination area k of theillumination beam. The matrix B may be representative of a commandmatrix. The matrix s may be representative of the wavefront shapemeasurement data in the first set of wavefront data. Each wavefrontshape element s_(i), may be associated with the wavefront shapeinformation associated with element i and may be representative of awavefront shape in the particular wavefront detection area. Eachillumination area k may be in an optically conjugate position with aparticular set of one or more wavefront detection areas. The matrix G₃may be representative of the local gain based upon the statusmeasurement data in the wavefront data. Each local gain element G₃ _(k)may be calculated based on one or more status measurement dataassociated with the particular set of one or more wavefront detectionareas that are in the optically conjugate position with the illuminationarea k; and the value G₁ may be representative of global gain.

In some embodiments the first set of wavefront data may include mwavefront elements. The local gain may include a set of m local gainvalues. Each local gain value i may be applied to a correspondingwavefront shape information element i during the calculation of thesecond set of control data.

In some embodiments, the second set of control data may include ncontrol elements. The local gain may include a set of n local gainvalues. Each local gain value k may be used to calculate a correspondingcontrol element k.

In some embodiments, the status measurement data for each particularwavefront element may be representative of a signal intensity associatedwith data used to calculate the wavefront shape measurement data in theparticular area of the received beam of light associated with theparticular wavefront element.

In some embodiments, the status measurement data for each particularwavefront element may be an estimate of a diameter of a spot associatedwith information used to calculate the shape of the wavefront in theparticular area of the received beam of light associated with particularwavefront element.

In some embodiments the adaptive optics scanning laser ophthalmoscopebeing controlled may include a Shack-Hartmann sensor that may be used toproduce the first set of wavefront data. Each particular wavefrontelement in the first set of wavefront data may be associated with aparticular lenslet in the Shack-Hartmann sensor. The status measurementdata for each particular wavefront element may be an estimate of adiameter of a spot associated with information used to calculate thewavefront shape measurement data.

In some embodiments, a non-transitory computer readable medium encodedwith instructions for a controller to control an adaptive opticsscanning laser ophthalmoscope.

In some embodiments, a controller for controlling an adaptive opticsscanning laser ophthalmoscope, the controller comprising: a memory; anda processor. The processor may receive from the ophthalmoscope a firstset of wavefront data comprising a plurality of wavefront elements. Theprocessor may store first set of wavefront data in the memory. Eachparticular wavefront element may be associated with a particular area ofa received beam of light received from a fundus being imaged by theophthalmoscope. Each particular wavefront element may include wavefrontshape measurement data. The wavefront shape measurement data may berepresentative of a shape of a wavefront of the received beam of lightin a particular area of the received beam of light. Each particularwavefront element may include status measurement data. The statusmeasurement data may be a confidence indicator of ability of thewavefront shape measurement data to represent the shape of the wavefrontof the received beam of light in the particular area of the receivedbeam of light with a particular level of accuracy. The processor maycalculate a second set of control data based on the wavefront shapemeasurement data in the wavefront data and a third set of local gain.The third set of local gain may include a plurality of local gainelements. Each element among the plurality of local gain elements may beadjusted based on one or more of the status measurement data. Theprocessor transmits the second set of control data to theophthalmoscope. The ophthalmoscope uses the second set of control datato adjust a shape of an illumination wavefront of an illumination beamused to illuminate the fundus.

In some embodiments, the controller further comprises the adaptiveoptics scanning laser ophthalmoscope controlled by the controller. Insome embodiments, the controller further comprises a wavefront sensor.In some embodiments, the wavefront sensor may be a Shack-Hartmannsensor. In some embodiments, the controller further comprises awavefront adjustment device. In some embodiments, the wavefrontadjustment device may be a deformable mirror. In some embodiments, thewavefront adjustment device may include at least one liquid crystalelement. In some embodiments, the wavefront adjustment device mayinclude at least one spatial phase modulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments.

FIG. 1 is a generalized illustration of an apparatus in which anembodiment may be implemented.

FIG. 2 is an illustration of a controller that may be used in anembodiment.

FIGS. 3A-D are generalized illustrations of a wavefront sensor andHartmann spots as might be used in an embodiment.

FIGS. 4A-D are examples of wavefront spots as detected by a wavefrontsensor.

FIGS. 5A-B are illustrations of how a pinhole may be used in combinationwith a wavefront sensor.

FIGS. 6A-E are examples of wavefront spots as detected by a wavefrontsensor.

FIGS. 6F-G are illustrations of a lenslet array of a wavefront sensor isilluminated.

FIG. 6H is an illustration of the spatial correspondence of a wavefrontsensor and wavefront adjustment device.

FIG. 7 is an illustration of a method that may be implemented in anembodiment.

FIGS. 8A-B are illustrations of portions of a method that may beimplemented in an embodiment.

FIGS. 9A-C are illustrations of calculation methods.

DESCRIPTION OF THE EMBODIMENTS

Embodiments will be described below with reference to the attacheddrawings. Like numbers refer to like elements throughout. Exemplaryembodiments will be described in detail with reference to the drawingsbelow. It shall be noted that the following description is merelyillustrative and exemplary in nature, and is in no way intended to limitthe disclosure and its applications or uses. The relative arrangement ofcomponents and steps, numerical expressions and numerical values setforth in the embodiments do not limit the scope of the disclosure unlessit is otherwise specifically stated. Techniques, methods, and deviceswhich are well known by individuals skilled in the art may not have beendiscussed in detail since an individual skilled in the art would notneed to know these details to enable the embodiments discussed below.Further, an image photographing apparatus as disclosed in the followingwhich is used to inspect an eye as described below may also be used toinspect other objects including but not limited to skin, and internalorgans.

Ophthalmoscope

A first embodiment is described with reference to a fundus imagephotographing apparatus (ophthalmoscope) such as the photographingapparatus illustrated in FIG. 1.

Embodiments are directed towards systems, methods, non-transitorycomputer readable medium, and software which are used in connection withan imaging system such as an ophthalmoscope 100. FIG. 1 is anillustration of an exemplary ophthalmoscope 100. An ophthalmoscope 100is a system or apparatus for obtaining information about an interiorportion of the eye 111 (e.g., the fundus).

An exemplary embodiment may be a scanning ophthalmoscope. A scanningophthalmoscope scans a spot across the eye 111. The spot may be a spotof light from a light source 101 that is scanned across the eye 111.

In an exemplary embodiment 100, the spot of light is produced by a lightsource 101. The light source 101 may be incorporated into theophthalmoscope 100; alternatively, the ophthalmoscope 100 may include aninput for receiving the light source 101. The input for the light source101 may be a fiber optic input 102 or a free space input (not shown).The light source 101 may be a laser, a broadband light source, ormultiple light sources. In an exemplary embodiment, the light source 101is a super luminescent diode (SLD) light source having a wavelength of840 nm. The wavelength of the light source 101 is not particularlylimited, but the wavelength of the light source 101 for fundus imagephotographing is suitably set in a range of approximately 800 nm to1,500 nm in order to reduce glare perceived by a person being inspectedand to maintain imaging resolution.

In an exemplary embodiment, light emitted from the light source 101passes through a single-mode optical fiber 102, and is radiated ascollimated light (measuring light 105) by a collimator 103.

In an exemplary embodiment, the polarization of the irradiated light maybe adjusted by a polarization adjusting member 119 (not shown) providedin a path of the single-mode optical fiber 102. In an alternativeconfiguration, the light source 101 is polarized and single-mode opticalfiber 102 is polarization maintaining fiber. In another configuration,the polarization adjusting member may be placed after the collimator103. Alternatively, the polarization adjusting member may be replacedwith a polarizer. In an alternative embodiment, the irradiated light maybe unpolarized, depolarized, or the polarization may be uncontrolled.

The measuring light 105 radiated from the collimator 103 passes througha light division portion 104 including a beam splitter. An exemplaryembodiment includes an adaptive optical system.

The adaptive optical system may include a light division portion 106, awavefront sensor 115, wavefront adjustment device 108, a pinhole 119, alens 122, a lens 123, and reflective mirrors 107-1 to 107-4 for guidingthe measuring light 105 to and from those components. The reflectivemirrors 107-1 to 107-4 are provided to guide the measuring light 105 toand from the pupil of an eye 111, the wavefront sensor 115, and thewavefront adjustment device 108. The reflective mirrors may be replacedwith suitable optics, such as lenses and/or apertures. Likewise, thelenses may be replaced with mirrors. The wavefront sensor 115 and thewavefront adjustment device 108 may be in an optically conjugaterelationship. A beam splitter may be used as the light division portion106. The wavefront sensor 115 may be a Shack-Hartmann sensor or othertype of sensor that gathers information that is representative on thespatial nature of the wavefront of light coming from the subject. Otherexamples of types of sensors that provide information about the shape ofa wavefront include but are not limited to: a pyramid wavefront sensor;common path interferometer; Foucault knife-edge tester; a multilateralshearing interferometer; Ronchi tester; and Shearing Interferometer.

A pinhole 121 and lenses 122 and 123 may be placed between the wavefrontsensor 115 and the beam splitter 106. The pinhole 121, lens 122, andlens 123 are arranged to ensure that light from the surface of theretina is detected by the wavefront sensor 115 while other light isblocked. Lenses 122-123 may be replaced with mirrors.

The measuring light 105 passing through the light division portion 106is reflected by the reflective mirrors 107-1 and 107-2 so as to enterthe wavefront adjustment device 108. The measuring light 105 isreflected by the wavefront adjustment device 108 and is furtherreflected by the reflective mirrors 107-3 and 107-4.

The wavefront adjustment device 108 maybe a transmissive device or areflective device. The wavefront adjustment device 108, may be anaddressable spatial light phase modulator that allows relative phasesacross a beam coming into the wavefront adjustment device 108 to beadjusted such that relative phases across the beam coming out of thewavefront adjustment device 108 are adjustable. In an exemplaryembodiment, one or two spatial phase modulators each including a liquidcrystal element is used as the wavefront adjustment device 108. Theliquid crystal element may modulate a phase of only a specific polarizedcomponent. In which case, two liquid crystal elements may be employed tomodulate substantially orthogonal polarized components of the measuringlight 105. In an alternative embodiment, the wavefront adjustment device108 is a deformable mirror.

The measuring light 105 reflected off mirror 107-4 is two-dimensionallyscanned by a scanning optical system 109. In an exemplary embodiment,the scanning optical system 109 includes a first scanner 109-1 and asecond scanner 109-2. The first scanner 109-1 rotates around the firstaxis, while the second scanner 109-2 rotates around a second axis. Thefirst axis is substantially orthogonal to the second axis. Substantiallyin the context of the present disclosure means within the alignment andmeasurement tolerances of the system. The scanning optical system 109may include one or more additional scanners 109-3 (not shown) which areused for steering the scanning area to different parts of the fundus.

FIG. 1 illustrates the first scanner 109-1 rotating in the x-y plane,while the second scanner 109-2 is rotating in the z-x plane. In thecontext of the present disclosure, rotating the measuring light 105 in afirst plane around the first axis is equivalent to rotating themeasuring light 105 in the first plane and is equivalent to scanning thespot of light in the main scanning direction or the lateral direction ofthe object being imaged. In the context of the present disclosure,rotating the measuring light 105 in a second plane around the secondaxis is equivalent to scanning the spot of light in the sub-scanningdirection or the longitudinal direction of the object being imaged. Thesub-scanning direction is substantially orthogonal to the main scanningdirection.

A scanning period of the first scanner 109-1 is less than the scanningperiod of the second scanner 109-2. The order of the first scanner 109-1and the second scanner 109-2 may be exchanged without impacting theoperation of an exemplary embodiment. The first scanner 109-1 mayoperate in a resonant scanning mode.

In an exemplary embodiment, the scanning optical system 109 may be asingle tip-tilt mirror that is rotated around the first axis and aroundthe second axis that is substantially orthogonal to the first axis. Anexemplary embodiment may also use non-mechanical beam steeringtechniques.

In an exemplary embodiment, the first scanner 109-1 and the secondscanner 109-2 are galvano-scanners. In another exemplary embodiment, oneof the first scanner 109-1 and the second scanner 109-2 is a resonantscanner. The resonant scanner may be used for the main scanningdirection. The resonant scanner may be tuned to oscillate at a specificfrequency. There may be additional optical components, such as lenses,mirrors, apertures, and etc. between the scanners 109-1, 109-2, andother optical components. These additional optical components may bearranged such that the light is focused onto the scanners, in a mannerthat is optically conjugate with all of or one or more of the subject111, the wavefront adjustment device 108, the wavefront sensor 115, anda detector 114.

The measuring light 105 scanned by the scanning optical system 109 isradiated onto the eye 111 through eyepieces 110-1 and 110-2. Themeasuring light radiated to the eye 111 is reflected, scattered, orabsorbed by the fundus 111. When the eyepieces 110-1 and 110-2 areadjusted in position, suitable irradiation may be performed inaccordance with the diopter of the eye 111. Lenses may be used for theeyepiece portion in this embodiment, but other optical components suchas spherical mirrors may also be used.

Light which is produced by reflection, fluorescence, and/or scatteringby a fundus of the eye 111 then travels in the reverse direction alongthe same path as the incident light. A part of the reflected light isreflected by the light division portion 106 to the wavefront sensor 115to be used for measuring a light beam wavefront.

In an exemplary embodiment, a Shack-Hartmann sensor is used as thewavefront sensor 115. However, an exemplary embodiment is not limited toa Shack-Hartmann sensor. Another wavefront measurement unit, forexample, a curvature sensor may be employed or a method of obtaining thewavefront by reverse calculation from the spot images may also beemployed.

In FIG. 1, when the reflected light passes through the light divisionportion 106, a part thereof is reflected on the light division portion104 and is guided to a light intensity sensor 114 through a collimator112 and an optical fiber 113. The light intensity sensor 114 convertsthe light into an electrical signal. The electrical signal is processedby a PC 117 or other suitable processing device into an image of thesubject and the image is displayed on a display 118.

The wavefront sensor 115 is connected to an adaptive optics controller116. The received wavefront is transferred to the adaptive opticscontrol unit 116. The wavefront adjustment device 108 is also connectedto the adaptive optics control unit 116 and performs modulation asinstructed by the adaptive optics control unit 116. The adaptive opticscontroller 116 calculates a modulation amount (correction amount) toobtain a wavefront having less aberration based on the wavefrontobtained by a measuring result of the wavefront sensor 115, andinstructs the wavefront adjustment device 108 to perform the modulationaccording to the modulation amount. The wavefront measurement and theinstruction to the wavefront adjustment device are repeated and afeedback control is performed so as to obtain a suitable wavefront.

In an exemplary embodiment the light division portions 104 and 106 arepartially reflective mirrors. In an alternative exemplary embodiment,the light division portions 104 and/or 106 may include fused fibercouplers. In another alternative exemplary embodiment, the lightdivision portions 104 and/or 106 may include dichroic reflectors, inwhich case a different wavelength of light is used for obtaining animage of the fundus then is used for detecting the spatial phase imagethat controls the adaptive optics system.

The detector 114 may detect reflections or fluorescence associated withthe scanning spot. The detection system may make use confocal microscopytechniques in which an aperture associated with the scanning spot isused to increase the resolution and/or contrast of the detection system.

The adaptive optics system described above includes at least thewavefront sensor 115 and the wavefront adjustment device 108 so that theaberration of the subject's eyes can be measured and compensated for. Adeformable mirror (DM) or a spatial light phase modulator (SLM) can beused as the wavefront adjustment device 108. Since the typical SLM has alarge number of actuators, it can modulate wavefront more precisely thanDM can. A liquid crystal on silicon spatial light modulator (LCOS-SLM)may be used as the wavefront adjustment device 108. The LCOS-SLM 108 canbe controlled to provide a precise spatial modulation of the phase ofthe beam that is used to illuminate the subject.

Controller

FIG. 2 is an illustration of the PC 117 and controller 116 that may beused in an embodiment. The controller 116 receives input values andoutputs control values. The controller 116 may be a general purposecomputer, a device specifically designed to controller theophthalmoscope or measuring instrument, or a hybrid device that usessome custom electronics along with a general purpose computer 117. Theinput values and control values maybe digital values or analog values.The controller 116 may include an analog to digital converter (ADC) anda digital to analog converter (DAC). The input values may include onemore values such as a signal from the wavefront sensor 115, a signalfrom the detector 114, and one or more values from one or more othersensors. The control values may include control values sent to awavefront adjustment device 108 and values to one or more of thescanners 109-1, 109-2. The control values may include additional valuesto other components of the instrument.

The controller 116 includes a processor 224-1. The processor 224-1 maybe a microprocessor, a CPU, an ASIC, a DSP, and/or a FPGA. The processor224-1 may refer to one or more processors that act together to obtain adesired result. The controller 116 may include a memory 226-1. Thememory 226-1 may store calibration information. The memory 226-1 mayalso store software for controlling the ophthalmoscope. The memory 226-1may take the form of a non-transitory computer readable storage medium.The non-transitory computer readable storage medium may include, forexample, one or more of a hard disk, a random-access memory (RAM), aread only memory (ROM), a distributed storage system, an optical disk(CD, DVD or Blu-Ray Disc, a flash memory device, a memory card, or thelike. The controller 116 may include input devices such as a keyboard, amouse, a touch screen, knobs, switches, and/or buttons.

The controller 116 may be connected to a computer (PC) 117 via a directconnection, a bus, or via a network. The computer 117 may include inputdevices such as a keyboard, a mouse, and/or a touch screen. The computer117 may be connected to a display 118. The results and/or data producedby the ophthalmoscope 100 may be presented to a user via the display118. The PC may include a processor 224-2, a memory 226-2. The PC mayalso include one or more GPUs 120

Adaptive Optics

Adaptive optics systems are typically controlled using a feedback looptype system. In these AO feedback loops aberrations are measured andthen the aberrations are corrected are processed one after anothercontinuously.

FIGS. 3A-B are illustrations of a Shack-Hartmann type wavefront sensor115 which may be used in an embodiment. FIG. 3A is a side view of theShack-Hartmann type wavefront sensor 115. FIG. 3B is a top view of theShack-Hartmann type wavefront sensor 115. The Shack-Hartmann typewavefront sensor 115 may include a CCD sensor 330 and a lenslet array328 just in front of the CCD sensor 330. The lenslet array 328 is anarray of lenslets 328-1. The light 305 from the subject 11 goes throughthe lenslet array 328 to divide the light into multiple portions of thelight. The divided light is then focused onto the surface of the CCDsensor 330 by the lenslet-array 328.

Low aberrated light from a low aberration eye can shape small spots 324on the CCD sensor surface 330 of the wavefront sensor 115 as illustratedin FIG. 3C. When the spots 332 are small, it is easy to detect a center(or centroid) of the intensity of the spots and to calculate the shapeof the wavefront. If the light is aberrated, the spots 332 get blurred,and it can be difficult to detect the center (or centroid) of theintensity as illustrated in FIG. 3D.

FIG. 4A is an illustration of a Hartmann image from a normal eye and atarget illustrating an estimated location of the pupil based on theHartmann image. FIG. 4B is an illustration of a Hartmann image from amyopic eye and a target illustration an estimated location of the pupilbased on the Hartmann image, and a target illustrating a relativelocation of the illumination beam based upon the system alignment. FIG.4C is a zoomed in image of 9 spots from the Hartmann image of a normaleye. FIG. 4D is a zoomed in image of 9 spots from the Hartmann image ofa myopic eye.

The wavefront sensor 115 produces measured aberration information whichis used in an AO feedback control loop as used in an embodiment. Themeasured aberration information may take the form of displacement data.That displacement data may be converted to one or more Zernikecoefficients. These Zernike coefficients may then be converted intocommand values for the wavefront adjustment device 108.

The displacement information s may also be directly used to generatecommand values x for the wavefront adjustment device 108. Generating thecommand values x may include the use of an Influence Function A whichrepresents a displacement matrix related to each actuator movement (orpixel) of the wavefront adjustment device 108 as described by equation(1). In which s is the displacement information based upon the measuredwavefront sensor signal. In which A is the Influence function. In whichx is the command values sent to the wavefront adjustment device 108.

s=Ax  (1)

Generating the command values may also include the use of a CommandMatrix B which is the pseudo inverse of the Influence Function A asdescribed equation (2). In which, the matrix B is the command matrix.

B=A ⁺  (2)

The command values x may be generated by multiplying the measureddisplacement information s by the Command Matrix B. In order tostabilize the AO control loop and prevent under or over correction anappropriate gain parameter G may be applied to the command values thewavefront adjustment device 108 as describe in equation (3). In which, Gis the gain parameter. Equation (3) represents an AO control loop whichuses an open loop control system. AO feedback control may also useclosed loop control, in which case the calculated command value iscombined with the previous command value. In this case, the gainparameter G may be 1 the first time the command values x are calculated.Equation (3) can be modified to describe a close loop control systemusing equation (3′).

x=GBs  (3)

x _(n) =GBs _(n) +x _(n-1)  (3′)

To improve the accuracy of the wavefront measurement, the pinhole 121may be placed in front of the wavefront sensor 115 to block light comingfrom surfaces other than the retina especially from the cornea asillustrated in FIG. 5B. This pinhole can also block the back reflectionlight from other optical elements in the optical system. FIGS. 5A-B aregeneralized illustrations of such a system. FIG. 5A illustrates thesubject 111 such as an eye being imaged by a system that includes awavefront sensor 115. The pinhole 121 is placed between the subject 111and the wavefront sensor 115. The pinhole 121 also placed between 2lenses 122 and 123. The pinhole 121 is positioned between 2 lenses 122and 123 such that extraneous light does not reach the wavefront sensor115. The size of the pinhole is such that it blocks light from thecornea as illustrated in FIG. 1B. The pinhole 121 allows light to passmainly from the retina of the subject 111 as illustrated in FIG. 1A. Thewavefront measurement is very important part of this feedback loopbecause if the wavefront is measured incorrectly, the wavefrontcorrector does not compensate for the real aberration and may generatean additional aberration. Sometimes the wavefront measurement isdisturbed by various factors. Direct reflection light from the surfaceof the cornea, cataract, pupil shrinking, eye lash and eye lid are mainreasons for disturbing the aberration measurement. Reflection light fromthe cornea can be blocked by a pinhole 121 in front of the Shack-Hartmansensor as illustrated in FIG. 5B.

The pinhole 121 is not a perfect solution to this problem, and strongdisturbing signal can be detected in some case. For example, FIG. 6A isan illustration of a Hartmann image in which the reflection from thecornea can be seen. Cataracts can also decreases spots signal in theHartmann image as illustrated in FIG. 6B. Even under normal measurementconditions, spot signals at the edge may be weaker than spot signals atthe center as illustrated in FIG. 6C. FIG. 6D is a zoomed in image ofsome Hartmann spots at the center of the Hartmann image. FIG. 6E is azoomed in image of some Hartmann spots at the edge of the Hartmannimage.

One reason for this lower intensity at the edge as illustrated in FIG.6E is because only a limited area of a lenslet 328-1 may be illuminatedby the incident light near the edge of wavefront sensor 115. On theother hand, the whole area of lenslet 328-1 is illuminated at the centerof the wavefront sensor 115. FIG. 6F is an illustration of the normalillumination of the lenslet array 328 with incident light 305. In FIG.6F a center lenslet 328-2 is fully illuminated and an edge lenslet 328-3is partially illuminated. FIG. 6G is another illustration of the normalillumination of the lenslet array 328 with the incident light. In FIG.6G another center lenslet 328-2 is fully illuminated and another edgelenslet 328-3 is partially illuminated. FIG. 6G also shows the sideprofile of the edge illumination and how a partially illuminated lenslet328-3 would be measured by the CCD sensor 330 when compared to the sameillumination of a fully illuminated lenslet 328-2.

As the intensity of the spot signal is decrease, then the influence ofnoise increases. To calculate the displacement, center of intensity iscalculated first. But if the illumination is not uniform, calculation ofthe center of intensity is not accurate. As a result, spot displacementat weaker illuminated area is not as accurate as one of a fullyilluminated area. It makes wavefront measurement incorrect and makes AOcontrol less precise and unstable.

In an embodiment the local gain of the AO control is adjusted accordingto the Shack-Hartman sensor spots' condition. An embodiment may make useof 2 gain parameters: G₁ and G₂. G₁ is a scaler value for entire AOcontrol loop. G₂ is an array of values G₂=[g₁ . . . g_(m)] wherein m isnumber of lenslets 328-1 in the lenslet array 328. The array G₂ is amatrix which consists of local gain values for each spot in theShack-Hartman sensor 115. Equation (4) described G₁ may be applied toequation (3).

x=G ₁ Bs  (4)

The values x, B, and s are matrices in most cases, and can be describedusing equation (5).

$\begin{matrix}{\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\\vdots \\x_{n}\end{bmatrix} = {{G_{1}\begin{bmatrix}B_{1,1} & B_{1,2} & B_{1,3} & \cdots & B_{1,m} \\B_{2,1} & B_{2,2} & B_{2,3} & \cdots & B_{2,m} \\B_{3,1} & B_{3,2} & B_{3,3} & \cdots & B_{3,m} \\\ldots & \ldots & \ldots & \ddots & \ldots \\B_{n,1} & B_{n,2} & B_{n,3} & \cdots & B_{n,m}\end{bmatrix}}\begin{bmatrix}s_{1} \\s_{2} \\s_{3} \\\vdots \\s_{m}\end{bmatrix}}} & (5)\end{matrix}$

In which n is the number of actuators or pixels in the wavefrontadjustment device 108, and the matrix x includes a set of control valuesx₁. In which m is the number of lenslets or their equivalents associatedwith the wavefront sensor 115, and the matrix s includes a set ofmeasured wavefront sensor signal value s_(j). The measured wavefrontsensor signal value s_(j) is the displacement associated with each spotj, lenslet j or their equivalent. The measured wavefront sensor signalvalue s_(i) may be a displacement value or a slope that includes 2values s_(j)=[s_(j) _(x) s_(j) _(y) ]. The command matrix B may be a n×mmatrix as shown in equation (5). The command matrix includes commandsB_(i,j), which are calculated in the manner described above.

In an embodiment the gain of the AO control is adjusted according to thewavefront sensor's local condition as described by equation (6).

x=G ₁ B(sG ₂)  (6)

Equation (6) is substantially similar to equations (4)-(5) and includesthe additional use of a matrix G₂ which may be used to represent thelocal gain associated with each spot. The matrix G₂ may be a diagonalmatrix with m local gain elements G₂ _(j) associated with each spot j asillustrated in following rewritten version of equation (6) in which thematrix elements are specifically identified.

$\begin{matrix}{\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\\vdots \\x_{n}\end{bmatrix} = {{G_{1}\begin{bmatrix}B_{1,1} & B_{1,2} & B_{1,3} & \cdots & B_{1,m} \\B_{2,1} & B_{2,2} & B_{2,3} & \cdots & B_{2,m} \\B_{3,1} & B_{3,2} & B_{3,3} & \cdots & B_{3,m} \\\ldots & \ldots & \ldots & \ddots & \ldots \\B_{n,1} & B_{n,2} & B_{n,3} & \cdots & B_{n,m}\end{bmatrix}}\left( {\begin{bmatrix}s_{1} \\s_{2} \\s_{3} \\\vdots \\s_{m}\end{bmatrix}\begin{bmatrix}G_{2_{1}} & 0 & 0 & \ldots & 0 \\0 & G_{2_{2}} & 0 & \ldots & 0 \\0 & 0 & G_{2_{3}} & \ldots & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \ldots & G_{2_{m}}\end{bmatrix}} \right)}} & (6)\end{matrix}$

The value G₂ _(j) is determined by the quality metric (confidenceindicator) of the displacement information such as one or more of: anillumination intensity associated with each spot; a size of each spot;and a signal to noise ratio (S/N) associated with each spot. Eachquality metric or confidence indicator is an example of statusmeasurement data that can be used to indicate the quality of the datathat is then used to calculate the shape of the wavefront. Many methodsmay be used for calculating G₂ _(j) based on one or more quality metricssuch as the one listed above or other quality metrics. FIGS. 9A-C areexamples of the calculation methods. The X axis of the graphs in FIGS.9A-C represents the relative intensity I_(j) of each spot relative tothe saturation value I_(maximum) of the CCD sensor. The Y axisrepresents a local gain value G₂ _(j) for each spot. Equation (7) is anillustration of how G₂ _(j) may be described in terms of atransformation function ƒ that is dependent upon one or more of thequality metrics such as the intensity I_(j) of each spot. FIG. 9A is anillustration in which the transformation function ƒ is a linear functionas described by equation (7A). FIG. 9B is also an illustration of asimple linear function ƒ described by equation (7B), but it saturates at50% (or some other value) of the because 50% of the saturation value mayprovide a high enough quality signal such that there is high confidencein the quality of the displacement calculation. FIG. 9C is anillustration in which the G₂ _(j) may be calculated using look up tablesuch that the transformation function ƒ is a staircase function.Equation (7C) is an example of such a look up table. The intensity I_(j)may be the peak intensity of the spot j or the mean intensity of thespot j. The transformation function ƒ may be a function other qualitymetrics instead of the intensity I_(j) such as the diameter of the spotj; a shape of spot j; or S/N associated with each spot j. Thetransformation function ƒ may also be a function of multiple qualitymetrics.

$\begin{matrix}{G_{2_{j}} = {f\left( I_{j} \right)}} & (7) \\{G_{2_{j}} = {{f\left( I_{j} \right)} = \frac{I_{j}}{I_{maximum}}}} & \left( {7A} \right) \\{G_{2_{j}} = {{f\left( I_{j} \right)} = \left\{ \begin{matrix}{{1\mspace{14mu} {if}\mspace{14mu} I_{j}} > \frac{I_{maximum}}{2}} \\{{\frac{2\; I_{j}}{I_{maximum}}\mspace{14mu} {if}\mspace{14mu} I_{j}} \leq \frac{I_{maximum}}{2}}\end{matrix} \right.}} & \left( {7B} \right) \\{\quad\begin{matrix}\frac{I_{j}}{I_{maximum}} & {G_{2_{j}} = {f\left( I_{j} \right)}} \\{0\text{-}10\%} & 0 \\{0\text{-}20\%} & 0.2 \\{0\text{-}30\%} & 0.5 \\{0\text{-}50\%} & 0.8 \\{50\text{-}100\%} & 1\end{matrix}} & \left( {7C} \right)\end{matrix}$

The wavefront sensor 115 of the ophthalmoscope 100 produces a set ofwavefront data. The wavefront data includes a plurality of wavefrontelements. Each wavefront element among the plurality of wavefrontelements is associated with a particular area of a received beam oflight received from a fundus 111 being imaged by the ophthalmoscope 100.Each wavefront element includes a plurality of components. Eachcomponent among the wavefront element represents a piece of informationabout the shape of the wavefront received from the fundus 111. A firstcomponent of the wavefront element is wavefront shape measurement data.The wavefront shape measurement data may be one or more values thatrepresent a shape of the wavefront in a particular area of the receivedbeam of light. Alternatively, the wavefront shape measurement data maybe one or more values that are used to calculate the shape of thewavefront the particular area of the received beam of light. A secondcomponent of the wavefront element is status measurement data. Thestatus measurement data is a confidence indicator of ability of thewavefront shape measurement data to represent the shape of the wavefrontof the received beam of light in the particular area of the receivedbeam of light with a particular level of accuracy. The statusmeasurement data represents information that is correlated with theaccuracy with which the wavefront sensor 115 represents the shape of thewavefront. The intensity of a Hartmann spot is an example of statusmeasurement data. The processor 224 receives the set of wavefront datafrom the as one chunk of data or as ophthalmoscope 100 or as a pluralityof chunks of data. The processor 224 may also receive wavefront datafrom the ophthalmoscope 100 which it then transforms into the wavefrontshape data and status measurement data.

Equation (8) is substantially similar to equation (6) and includes theadditional use of a matrix G₃ instead of matrix G₂ which may be used torepresent the local gain associated with each spot. The matrix G₃ may bea diagonal matrix with n local gain elements G₃ ₃ associated with eachactuator i or pixel i.

$\begin{matrix}{{\mspace{20mu} {x = {{{G_{1}({Bs})}{G_{3}\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\\vdots \\x_{n}\end{bmatrix}}} = {G_{1}\left( {\left\lbrack \begin{matrix}B_{1,1} & B_{1,2} & B_{1,3} & \cdots & B_{1,m} \\B_{2,1} & B_{2,2} & B_{2,3} & \cdots & B_{2,m} \\B_{3,1} & B_{3,2} & B_{3,3} & \cdots & B_{3,m} \\\ldots & \ldots & \ldots & \ddots & \ldots \\B_{n,1} & B_{n,2} & B_{n,3} & \cdots & B_{n,m}\end{matrix} \right\rbrack\left\lbrack \begin{matrix}s_{1} \\s_{2} \\s_{3} \\\vdots \\s_{m}\end{matrix} \right\rbrack} \right)}}}\quad}\left\lbrack \begin{matrix}G_{3_{1}} & 0 & 0 & \ldots & 0 \\0 & G_{3_{2}} & 0 & \ldots & 0 \\0 & 0 & G_{3_{3}} & \ldots & 0 \\\vdots & \vdots & \vdots & \ddots & \vdots \\0 & 0 & 0 & \ldots & G_{3_{n}}\end{matrix} \right\rbrack} & (8)\end{matrix}$

FIG. 6H is an illustration of a wavefront sensor 115 overlay with anillustration of the wavefront correction device 108. The wavefrontsensor 115 and the wavefront correction device 108 are not co-locatedwith each other but they are located at optically conjugate planeswithin the ophthalmoscope 100 as illustrated in FIG. 1. FIG. 6H is anillustration of how an internal components of the wavefront sensor 115and internal components of the wavefront correction device 108 arecorrelated with each on their corresponding conjugate planes.

In the example illustrated in FIG. 6H the wavefront sensor 115 is aShack-Hartmann Sensor, this is a non-limiting example. FIG. 6Hillustrates the relative positions of each lenslet 328-1 as a circle.Each lenslet 328-1 produces a spot on the CCD 330. The relativedisplacement of each spot as detected by the CCD 330 is used tocalculate the shape of the wavefront.

In the example illustrated in FIG. 6H the wavefront correction device108 is a deformable mirror 108, this is a non-limiting example. Thedeformable mirror 108 includes a plurality of actuators, and a pluralityof mirrors (108-1 . . . 108-i . . . 108-n) associated with eachactuator. The border of each mirror 108-i is illustrated as a squarewith a thick black line. As illustrated in FIG. 6H a particular mirror108-1 is associated with particular lenslets 1 through 4 and aparticular mirror 108-2 is associated with particular lenslets 5-8.

The deformable mirror may be a segmented mirror or a flexible mirrormembrane. Segmented mirrors have limited cross talk so the influencefunction A and the corresponding command matrix B are simpler, but thereare edge effects due to the edges of the mirrors. While flexible mirrormembranes do not have edge effects they do have cross talk issues aschanging one portion of the mirror effects other portions of the mirrorwhich has an impact on the influence function A and the correspondingcommand matrix B. FIG. 6H illustrates a situation in which eachparticular is mirror is well aligned with a particular set of lenslets.This may not always be the case, alternatively, a particular lenslet maybe associated with multiple mirrors, such as when an edge of a mirrordoes not correlate with an edge of a lenslet. In an alternativeembodiment, the deformable mirror may be replaced with a spatial phasemodulator in which case, the thick black lines illustrate the edges ofpixels in the spatial phase modulator.

As illustrated in FIG. 6, each mirror 108-i is associated with aplurality of lenslets. Each actuator i, pixel i, or mirror 108-i is alsoassociated with a local gain element G₃ _(i) . Each local gain elementis calculated based on the spot illumination condition of the lensletsassociated with each spot. The spot illumination condition may includeone or more values such as the signal strength of the spot; signal tonoise ratio of the spot; and the spot size. Other metrics may also beused to represent the spot illumination condition. The method forcalculating G₃ ₃ may make use of a second transformation function thatis substantially similar to the transformation function ƒ described inequation (7). Except that the second transformation function is functionof quality metrics associated with multiple spots. The secondtransformation function may be a summation of the transformationfunction ƒ of several spots. The second transformation function may be astatistical value associated with the transformation function ƒ ofseveral spots. The second transformation function may be a separatefunction of one or more quality metrics associated with multiple spots.

For example the mirror 108-1 is associated with lenslets 1-4. Therefore,local gain element G₃ ₁ is associated with the spot illuminationcondition of lenslets 1-4. Likewise, local gain element G₃ ₂ isassociated with the spot illumination condition of lenslets 5-8, sincemirror 108-2 is associated with lenslets 5-8 as illustrated in FIG. 6H.As each local gain element G₃ _(i) is calculated based on metrics whichreflect the states of all of the spots formed by the lenslets associatedwith each local gain element.

Adaptive Optics (AO) Control Method

An embodiment may include an AO control method, non-transitory mediumencoded with instructions for performing the AO control method. Anembodiment may include one or more processors that perform the method.The one or more processors may include circuits or sets of instructionsfor performing the AO control method. An embodiment may include asubject inspection apparatus with an AO system that includes the AOcontrol method. An embodiment may include an eye inspection apparatuswith an AO system that includes the AO control method.

The AO Control method may include a step of measuring the spotdisplacement data and outputting the displacement information s.Measuring the spot displacement data may include identifying a set ofpositions each position will be a spot of light associated with eachlenslet. Each position may represent the relative position of the spotof light relative to center associated with a centerline of eachlenslet.

The AO control method may also include a step of measuring spotillumination condition associated with each spot. The spot illuminationcondition may include one more pieces of information that represent thecondition of each spot. The AO control method may also include a step ofcalculating the matrix G₂ of local gain values based on the measuredspot illumination condition. The spot illumination condition may includeone or more values such as the signal strength of the spot; signal tonoise ratio of the spot; and the spot size. Other metrics may also beused to represent the spot illumination condition.

The AO control method may also include calculating command values xbased on the displacement information s. The AO control method may alsoinclude calculating modified command values x based on the displacementinformation s and local gain G₂.

AO Control Flowchart

FIG. 7 is an illustration of a flowchart 700 that represents how anembodiment of the AO control method may be implemented by one or moreprocessor(s) 224. The processor(s) 224 may be a part of controller 116and/or a PC 117. The AO control method 700 may include a step 734 ofinitiating the start of the AO control method. The AO control method maybe initiated by a user or may be initiated automatically as part of thestartup procedure of an apparatus (e.g. ophthalmoscope 100) that makesuse of the AO control method 700. A part of step 734 may includereceiving instructions by a processor 224 to imitate the AO controlmethod and may including loading instructions and data into memory 226associated with the controller 116 and/or the PC 117.

The method 700 may include a step 736 of the processor 224 receivingaberration information about the subject, which may be an eye 111. Theaberration information may be received from the wavefront sensor 115.The method 700 may include a step 738 of calculating the command valuesx. The details of how the command values may be calculated are describedin the methods bellow. The command values x may be calculated by theprocessor(s) 224.

The method 700 may include a step 740 of sending the command values x tothe wavefront adjustment device 108. The wavefront adjustment device 108then adjusts the wavefront to compensate for the measured aberrations.The command values x may take the form of an adjustment value that isapplied to each mirror of a deformable mirror or a pixel of each spatialphase modulator. In an alternative embodiment, the command values x maytake the form of higher level descriptions of the aberration that needsto be compensated for such as Zernike coefficients for example.

The method 700 may include a step 742 of checking to see if AO controlmethod 700 should be stopped. If the AO control method 700 is not to bestopped, then the AO control method 700 moves back to step 736. If thecontrol method 700 is to be stopped, then the AO control method moves onto step 744 and the AO control method ends. The command to stop may bereceived from a user from an input device, via a computer, a controlswitch, or some other interface. Alternatively, the command to stop maybe received as a signal from the instrument being controlled by the AOcontrol method 700.

First Exemplary Method of Calculating Command Values

The AO control method 700 includes a predefined process 738. Thepredefined process 738 is a method of calculating command values 738-1.One method of implementing the predefined process 738 is illustrated asmethod 738-1 in FIG. 8A. The method 738-1 may include the step 846 ofstarting the method 738-1. The method 738-1 may include the step 848 ofobtaining the displacement information s. The method 738-1 may includethe step 850 of obtaining information that is indicative of the qualityof the displacement information such as one or more of: an illuminationintensity associated with each spot; a size of each spot; and a signalto noise ratio (S/N) associated with each spot. The method 738-1 mayinclude a step 852 of generating a local gain matrix G₂ based on theinformation obtained in step 850. For example, each of the local gainelements G₂ _(j) of G₂ may be calculated in accordance with theintensity of the spot relative to the average value of intensities ofall the illuminated spots. This may generate a wide variety of valuesfor the elements in G₂. A correction formula such as the followingequation (9) may be used to narrow the range of values

G_(2_(j_(new))).

Other alternative methods may also be used to adjust the range valuesfor the elements in G₂. The method 738-1 may include a step 854 ofcalculating the command values x based on equation (6). The method 738-1may end in a step 856. The step 856 may include transmitting commandvalues x from the processor 224 to the wavefront adjustment device 108.Transmitting the command values x may include adding new command valuesx to old command values x and sending the sum of the old and new valuesfrom the processor 224 to the wavefront adjustment device 108.

$\begin{matrix}{G_{2_{j_{new}}} = \frac{G_{2_{j}} + {\sum\limits_{k = 1}^{m}\; G_{2_{k}}}}{2{\sum\limits_{k = 1}^{m}\; G_{2_{k}}}}} & (9)\end{matrix}$

Second Exemplary Method of Calculating Command Values

A second exemplary method of implementing the predefined process 738 isillustrated as method 738-2 in FIG. 8B. The method 738-2 includes manyof the same steps as method 738-1 including steps 846, 848, 850, and856. The description of steps 846, 848, 850, and 856 will not berepeated. The method 738-2 may include a step 858 of generating a localgain matrix G₃ based on the information obtained in step 850. Forexample, each of the local gain element s G₃ _(i) of G₃ may becalculated in accordance with the intensity of the spot relative to theaverage value of intensities of all illuminated spots. This may generatea wide variety of values for the elements in G₃. A correction formulasuch as the following equation (10) may be used to narrow the range ofvalues

G_(3_(i_(new)))

similar to equation 8. Other alternative methods may also be used toadjust the range values for the elements in G₃. The method 738-2 mayinclude a step 860 of calculating the command values x based on equation(8). The method 738-2 may end in a step 856.

$\begin{matrix}{G_{3_{i_{new}}} = \frac{G_{3_{i}} + {\sum\limits_{k = 1}^{n}\; G_{3_{k}}}}{2{\sum\limits_{k = 1}^{n}\; G_{3_{k}}}}} & (10)\end{matrix}$

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

1. (canceled)
 2. An ophthalmic apparatus having an adaptive optics system, the apparatus comprising: a detecting unit configured to detect each position data of a plurality of spots on a sensor surface and a status data of each spot of the plurality of spots, the plurality of spots being formed on the sensor surface by dividing return light from an eye to be examined by a lens array; a calculation unit configured to calculate a set of wavefront data using the each position data and a set of local gain data using the each status data, then obtain a set of a control data based on the set of wavefront data and the set of local gain data; and a wavefront adjustment unit configured to adjust the wavefront of the return light based on the set of control data.
 3. The apparatus according to claim 2, wherein the status data including at least one of an intensity associated with each spot; a size of each spot; and a signal to noise ratio (S/N) associated with each spot.
 4. The apparatus according to claim 2, further comprising: a light sensor unit configured to convert the return light adjusted by the wavefront adjustment unit to an electrical signal; and a generating unit configured to generate an image of the eye to be examined based on the electrical signal.
 5. The apparatus according to claim 2, wherein the set of local gain data is calculated using a transformation function that is dependent upon the each status data.
 6. The apparatus according to claim 2, wherein the apparatus includes an AO-SLO or an AO-OCT.
 7. The apparatus according to claim 2, wherein the detecting unit includes a Shack-Hartmann sensor.
 8. The apparatus according to claim 2, wherein the wavefront adjustment unit includes a deformable mirror.
 9. A method for controlling to control an ophthalmic apparatus having an adaptive optics system, the method comprising: detecting each position data of a plurality of spots on a sensor surface and a status data of each spot of the plurality of spots, the plurality of spots being formed on the sensor surface by dividing return light from an eye to be examined by a lens array; calculating a set of wavefront data using the each position data and a set of local gain data using the each status data; obtaining a set of a control data based on the set of wavefront data and the set of local gain data; and adjusting the wavefront of the return light based on the set of control data.
 10. A non-transitory computer readable medium encoded with instructions for a controller to control an ophthalmic apparatus having an adaptive optics system, comprising: instructions for detecting each position data of a plurality of spots on a sensor surface and a status data of each spot of the plurality of spots, the plurality of spots being formed on the sensor surface by dividing return light from an eye to be examined by a lens array; instructions for calculating a set of wavefront data using the each position data and a set of local gain data using the each status data; instructions for obtaining a set of a control data based on the set of wavefront data and the set of local gain data; and instructions for adjusting the wavefront of the return light based on the set of control data. 